* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  font: bold 20px "Courier";
}
#main {
  display: flex;
  width: 360px;
  height: 400px;
  background-color: #b7d4a8;
  border: 10px solid black;
  border-radius: 30px;
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  /* 50%为自身尺寸的一半 */
  flex-flow: column;
  align-items: center;
  justify-content: space-around;
}
#main #stage {
  width: 304px;
  height: 304px;
  border: 2px solid black;
  position: relative;
}
#main #stage #snake > div {
  width: 10px;
  height: 10px;
  background-color: black;
  border: 2px solid #b7d4a8;
  position: absolute;
}
#main #stage #food {
  width: 10px;
  height: 10px;
  background-color: black;
  border: 1px solid #b7d4a8;
  position: absolute;
  left: 40px;
  top: 100px;
  transform: rotate(45deg);
  display: flex;
  align-items: center;
  justify-content: center;
}
#main #panel {
  width: 300px;
  display: flex;
  justify-content: space-between;
}
